In recent years, in accordance with the diversification and microminiaturization of electronic devices, parts and the like, the developments of magnetic moldings having complicated forms or microstructures are intensily required in various technical fields.
Generally, moldings produced by pressing ferromagnetic powder such as ferrite powder and then sintering the pressed ferromagnetic powder at a high temperature of at least 1000.degree. C. are usually used. However, the moldings are largely contracted when the pressed ferromagnetic powder is sintered, and a great cost for producing is needed since the yield or the like is remarkably lowered when producing moldings having complicated forms or microstructures. Further, such magnetic moldings have many problems that it is difficult to be mechanically processed, that is, the obtained magnetic moldings are easily chipped off and brittle. Therefore, the developments of a resin-bonded magnetic composition having highly effective properties are required to solve these problems in various technical fields.
Hence, a known resin-bonded magnetic composition used as a magnetic core for a transformer and the like is produced by mixing iron powder or ferrite powder with resin components such as polyphenylene sulfide, epoxy resin, polyalkylene terephthalate, polyethylene, polypropylene, polybutene, polyvinyl chloride, ABS resin and AS resin and molding the mixture by hot-pressing.
However, since prior magnetic moldings produced by mixing resin components such as polyphenylene sulfide and epoxy resin and molding the mixture by hot-pressing have many problems in that the heat resistance is not sufficient, the mechanical strength is low and the initial magnetic permeability is low, the range of their uses is limited to a core of a coil used in a toy which does not need high reliabilities and high properties, and the like. Therefore, the fact is that the magnetic moldings have not yet been applied to industrial electronic devices and the like.
As the results of the present inventors' researches, the inventors have eventually found a resin-bonded magnetic composition having excellent heat resistance, moldability, mechanical workability, mechanical strength and initial magnetic permeability and a process for producing a magnetic molding from the magnetic composition, and the present invention was accomplished.